The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A100473 Numbers k such that 9*10^k + R_k + 6 is prime, where R_k = 11...1 is the repunit (A002275) of length k. 2
 1, 17, 23, 73, 131, 473, 685, 701, 1909, 3029, 3473, 4193, 9931 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers k such that (82*10^k + 53)/9 is a prime. Some of the larger entries may only correspond to probable primes. a(14) > 10^5. - Robert Price, Oct 25 2015 LINKS Table of n, a(n) for n=1..13. Makoto Kamada, Prime numbers of the form 911...117. Index entries for primes involving repunits. FORMULA a(n) = A100999(n) + 1. EXAMPLE n = 1, 17, so that 97 and 911111111111111117 are primes. MATHEMATICA Do[ If[ PrimeQ[(82*10^n + 53)/9], Print[n]], {n, 0, 10000}] (* Robert G. Wilson v, Jan 19 2005 *) CROSSREFS Cf. A002275, A100999. Sequence in context: A043142 A043922 A260179 * A060252 A127924 A250640 Adjacent sequences: A100470 A100471 A100472 * A100474 A100475 A100476 KEYWORD more,nonn AUTHOR Julien Peter Benney (jpbenney(AT)ftml.net), Nov 21 2004 EXTENSIONS a(8)-a(12) from Robert G. Wilson v, Jan 12 2005 a(13) from Robert G. Wilson v, Jan 12 2005 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 7 13:04 EDT 2024. Contains 375730 sequences. (Running on oeis4.)